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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>did:web Method Specification</title>
<script src="https://www.w3.org/Tools/respec/respec-w3c" async
class="remove"></script>
<script class="remove">
var respecConfig = {
specStatus: "CG-DRAFT",
shortName: "did-method-web",
wg: "Credentials Community Group",
wgURI: "https://www.w3.org/community/credentials/",
wgPublicList: "public-credentials",
editors: [{
name: "Michael Prorock",
url: "https://www.linkedin.com/in/mprorock/",
email: "mprorock@mesur.io",
company: "mesur.io",
companyURL: "https://mesur.io/"
},
{
name: "Orie Steele",
url: "https://www.linkedin.com/in/or13b/",
company: "Transmute",
companyURL: "https://www.transmute.industries/",
w3cid: 109171
},
{
name: "Oliver Terbu",
email: "oliver.terbu@consensys.net",
company: "Consensys",
companyURL: "https://consensys.net"
}],
authors: [
{
name: "Christian Gribneau",
email: "christian@gribneau.net",
company: "Ology Newswire, Inc.",
companyURL: "https://ology.com"
},
{
name: "Michael Prorock",
email: "mprorock@mesur.io",
company: "mesur.io",
companyURL: "https://mesur.io/"
},
{
name: "Orie Steele",
url: "https://www.linkedin.com/in/or13b/",
company: "Transmute",
companyURL: "https://www.transmute.industries/",
w3cid: 109171
},
{
name: "Oliver Terbu",
email: "oliver.terbu@consensys.net",
company: "Consensys",
companyURL: "https://consensys.net"
},
{
name: "Mike Xu",
email: "mike.xu@consensy.net",
company: "Consensys",
companyURL: "https://consensys.net"
},
{
name: "Dmitri Zagidulin",
email: "dzagidulin@gmail.com",
company: "Digital Bazaar",
companyURL: "https://digitalbazaar.com/"
}],
github: "https://github.com/w3c-ccg/did-method-web",
localBiblio: {
"DID-PRIMER": {
title: "DID Primer",
href: "https://github.com/WebOfTrustInfo/rebooting-the-web-of-trust-fall2017/blob/master/topics-and-advance-readings/did-primer.md",
authors: [
"Drummond Reed",
"Manu Sporny",
],
publisher: "Rebooting the Web of Trust 2017"
},
"OWASP-TRANSPORT": {
title: "Transport Layer Protection Cheatsheet",
href: "https://www.owasp.org/index.php/Transport_Layer_Protection_Cheat_Sheet",
}
},
};
</script>
</head>
<body>
<section id="abstract">
<p>
DIDs that target a distributed ledger face significant practical
challenges in bootstrapping enough meaningful trusted data around
identities to incentivize mass adoption.
We propose a new DID method using a web domain's existing reputation.
</p>
</section>
<section id="sotd">
</section>
<section>
<h1>
Introduction
</h1>
<section>
<h2>
Preface
</h2>
<p>
The Web DID method specification conforms to the requirements specified
in the Decentralized Identifiers v1.0 Specification [[DID-CORE]]. For
more information about DIDs and DID method specifications, please also
see the [[?DID-PRIMER]]
</p>
</section>
<section id="conformance">
<!-- This section is filled automatically by ReSpec. -->
</section>
<section>
<h2>
Examples
</h2>
<pre class="example"
title="Example did:web DID document using JSON Web Keys">
{
"@context": [
"https://www.w3.org/ns/did/v1",
"https://w3id.org/security/suites/jws-2020/v1"
],
"id": "did:web:example.com",
"verificationMethod": [
{
"id": "did:web:example.com#key-0",
"type": "JsonWebKey2020",
"controller": "did:web:example.com",
"publicKeyJwk": {
"kty": "OKP",
"crv": "Ed25519",
"x": "0-e2i2_Ua1S5HbTYnVB0lj2Z2ytXu2-tYmDFf8f5NjU"
}
},
{
"id": "did:web:example.com#key-1",
"type": "JsonWebKey2020",
"controller": "did:web:example.com",
"publicKeyJwk": {
"kty": "OKP",
"crv": "X25519",
"x": "9GXjPGGvmRq9F6Ng5dQQ_s31mfhxrcNZxRGONrmH30k"
}
},
{
"id": "did:web:example.com#key-2",
"type": "JsonWebKey2020",
"controller": "did:web:example.com",
"publicKeyJwk": {
"kty": "EC",
"crv": "P-256",
"x": "38M1FDts7Oea7urmseiugGW7tWc3mLpJh6rKe7xINZ8",
"y": "nDQW6XZ7b_u2Sy9slofYLlG03sOEoug3I0aAPQ0exs4"
}
},
],
"authentication": [
"did:web:example.com#key-0",
"did:web:example.com#key-2"
],
"assertionMethod": [
"did:web:example.com#key-0",
"did:web:example.com#key-2"
],
"keyAgreement": [
"did:web:example.com#key-1",
"did:web:example.com#key-2"
]
}
</pre>
<pre class="example"
title="Example did:web DID document using an ethereum address">
{
"@context": ["https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/secp256k1recovery-2020/v2"],
"id": "did:web:example.com",
"verificationMethod": [{
"id": "did:web:example.com#address-0",
"type": "EcdsaSecp256k1RecoveryMethod2020",
"controller": "did:web:example.com",
"blockchainAccountId": "eip155:1:0x89a932207c485f85226d86f7cd486a89a24fcc12"
}],
"authentication": [
"did:web:example.com#address-0"
]
}
</pre>
</section>
</section>
<section>
<h1>
Web DID Method Specification
</h1>
<section>
<h2>
Target system
</h2>
<p>
The target system of the Web DID method is the host (or domain if the
host
is not specified) name when the domain specified by the DID is resolved
through the Domain Name System (DNS).
</p>
</section>
<section>
<h2>
Method name
</h2>
<p>
The namestring that shall identify this DID method is: <code>web</code>.
A DID that uses this method MUST begin with the following prefix:
<code>did:web</code>. Per the DID specification, this string MUST be in
lowercase. The remainder of the DID, after the prefix, is specified
below.
</p>
</section>
<section>
<h2>
Method-specific identifier
</h2>
<p>
The method specific identifier is a fully qualified domain name that is
secured by a TLS/SSL certificate with an optional path to the DID
document. The formal rules describing valid domain name syntax are
described in [[RFC1035]], [[RFC1123]], and [[RFC2181]].
</p>
<p>
The method specific identifier MUST match the common name used in the
SSL/TLS certificate, and it MUST NOT include IP addresses. A port MAY be
included and the colon MUST be percent encoded to prevent a conflict
with paths. Directories and subdirectories MAY optionally be included,
delimited by colons rather than slashes.
</p>
<pre class="nohighlight">
web-did = "did:web:" domain-name
web-did = "did:web:" domain-name * (":" path)
</pre>
<pre class="example nohighlight" title="Example Web Method DIDs">
did:web:w3c-ccg.github.io
did:web:w3c-ccg.github.io:user:alice
did:web:example.com%3A3000
</pre>
</section>
<section>
<h2>
Key Material and Document Handling
</h2>
<p>
Due to the way most web servers present content, it is likely that a
particular `did:web` document will be served with a media type of
`application/json`. If a document is retrieved and it is named
`did.json`, a few processing rules should apply:
<ul>
<li>
If an
`@context` is present at the root of the JSON document,
the document should be processed according to the JSON-LD rules.
If this is not possible, or if the document fails processing, the
document should be rejected from consideration as a `did:web` doc.
</li>
<li>
If an
`@context` is present at the root of the JSON document,
and it passes JSON-LD processing, and it contains the context
`https://www.w3.org/ns/did/v1`, it may be further processed
as a
DID document as specified by section
<a href="https://www.w3.org/TR/did-core/#consumption-0">6.3.2</a> of
the
[[did-core]] specification.
</li>
<li>
If no
`@context` is present, it should be processed via normal
JSON rules for DID processing as specified in section
<a href="https://www.w3.org/TR/did-core/#consumption">6.2.2</a> of the
[[did-core]] specification.
</li>
</ul>
</p>
<p>
Whenever a DID URL is present within a `did:web` document, it must
be an absolute URL.
<p class="note">
This includes URLs inside of embedded key material and other metadata, and
prevents
key confusion attacks.
</p>
</p>
</section>
<section>
<h2>
DID method operations
</h2>
<section>
<p>
There is intentionally no HTTP API specified for did:web method
operations leaving programmatic registrations and management to be
defined by each implementation, or based on their own requirements in
their web environment.
</p>
</p>
<h3>
Create (Register)
</h3>
<p>
Creating a DID is done by:
</p>
<ol>
<li>
applying at a domain name registrar for use of a domain name and
</li>
<li>
storing the location of a hosting service, the IP address at a DNS
lookup service
</li>
<li>
creating the DID document JSON-LD file including a suitable keypair,
e.g. using the Koblitz Curve, and storing the <code>did.json</code>
file under the well-known URL to represent the entire domain, or
under the specified path if many DIDs will be resolved in this
domain.
</li>
</ol>
<p>
For example, for the domain name `w3c-ccg.github.io`, the `did.json`
will be available under the following URL:
</p>
<pre class="example nohighlight" title="Creating the DID">
did:web:w3c-ccg.github.io
-> https://w3c-ccg.github.io/.well-known/did.json
</pre>
<p>
If an optional path is specified rather the bare domain, the
<code>did.json</code> will be available under the specified path:
</p>
<pre class="example nohighlight"
title="Creating the DID with optional path">
did:web:w3c-ccg.github.io:user:alice
-> https://w3c-ccg.github.io/user/alice/did.json
</pre>
<p>
If an optional port is specified on the domain, the port colon
splitting the host and the port MUST be percent encoded to prevent
collision with the path.
</p>
<pre class="example nohighlight"
title="Creating the DID with optional path and port">
did:web:example.com%3A3000:user:alice
-> https://example.com:3000/user/alice/did.json
</pre>
</section>
<section>
<h3>
Read (Resolve)
</h3>
<p>
The following steps MUST be executed to resolve the DID document from
a Web DID:
</p>
<ol>
<li>
Replace ":" with "/" in the method specific identifier to obtain the
fully qualified domain name and optional path.
</li>
<li>
If the domain contains a port percent decode the colon.
</li>
<li>
Generate an HTTPS URL to the expected location of the DID document
by prepending <code>https://</code>.
</li>
<li>
If no path has been specified in the URL, append
<code>/.well-known</code>.
</li>
<li>
Append <code>/did.json</code> to complete the URL.
</li>
<li>
Perform an HTTP <code>GET</code> request to the URL using an agent
that can successfully negotiate a secure HTTPS connection, which
enforces the security requirements as described in <a
href="#security-and-privacy-considerations"></a>.
</li>
<li>
When performing the DNS resolution during the HTTP <code>GET</code>
request, the client SHOULD utilize [[RFC8484]] in order to prevent
tracking of the identity being resolved.
</li>
</ol>
</section>
<section>
<h3>
Update
</h3>
<p>
To update the DID document, the <code>did.json</code> has to be
updated. Please note that the DID will remain the same, but the
contents of the DID document could change, e.g., by including a new
verification key or adding service endpoints.
</p>
<p class="note">
Managing updates to the DID Document using a version control system
such as git and continious integration system such as GitHub Actions
can provide support for authentication and audit history.
</p>
<p class="note" title="HTTP API">
There is no HTTP API specified for the update process leaving
programmatic registrations and management to be defined by each
implementation.
</p>
</section>
<section>
<h3>
Deactivate (Revoke)
</h3>
<p>
To delete the DID document, the <code>did.json</code> has to be
removed or has to be no longer publicly available due to any other
means.
</p>
</section>
</section>
<section class="informative">
<h2>
Security and privacy considerations
</h2>
<section>
<h3>
Authentication and Authorization
</h3>
<p>
This DID method does not specify any authentication or authorization
mechanism for writing to, removing or creating the DID Document,
leaving it up to implementations to protect did:web documents as with
any other web resource.
</p>
<p>
It is up to implementer to secure their web environments according to
industry best practices for updating or otherwise managing web content
based on the specific needs of their threat environment.
</p>
</section>
<section>
<h3>
DNS Considerations
</h3>
<h4>
DNS Security Considerations
</h4>
<p>
DNS presents many of the attack vectors that enable active security
and privacy attacks on the did:web method and it's important that
implementors address these concerns via proper configuration of DNS.
For example, without proper security of the DNS resolution via <a
href="https://tools.ietf.org/html/rfc8484">DNS over HTTPS</a> it's
possible for active attackers to intercept the result of the DNS
resolution via a Man in the Middle attack which would point at a
malicious server with the incorrect DID Document.
</p>
<p>
Additionally, implementors should be aware of issues presented by a
Spoofed DNS records where the record returned by a malicious DNS
Server is inauthentic and allows the record to be pointed at a
malicious server which contains a different DID Document. To prevent
this type of issue, usage of DNSSEC which is
<a href="https://tools.ietf.org/html/rfc4033">RFC4033</a>,
<a href="https://tools.ietf.org/html/rfc4034">RFC4034</a>, and
<a href="https://tools.ietf.org/html/rfc4035">RFC4035</a>.
</p>
<h4>
DNS Privacy Considerations
</h4>
<p>
Due to the nature of the did:web method relying upon a DNS in order to
resolve the web server, all resolutions of a did:web identifier have
the potential to be tracked by a DNS provider. Additionally, due to
the DID Document being stored on a web server, each time the DID
Document resource is retrieved, the web server has the ability to
track the resolution of the DID Document. To mitigate the issue of the
relying party being tracked when resolving the DID Document the
relying party should look to either use a trusted universal resolver
service to gain herd privacy, utilize a VPN service or perform a
resolution over the TOR network. Another emerging solution that will
be useful to address this is <a
href="https://tools.ietf.org/html/draft-pauly-dprive-oblivious-doh-03">
draft-pauly-dprive-oblivious-doh-03</a>
</p>
</section>
<section>
<h3>
DID Document Integrity Verification
</h3>
<p>
Additional mechanisms such as <a
href="https://tools.ietf.org/html/draft-sporny-hashlink">Hashlinks</a>
MAY be utilized to aid in integrity protection and verification of the
DID document.
<br />
Under such a scenario the hash of the DID document could be recorded
to a trusted or distributed store and the retriever of the DID
document would generate a hash of the DID document in their posession
with the hash retrieved to ensure that no tampering with the DID
document had occurred.
</p>
</section>
<section>
<h3>
In-transit Security
</h3>
<p>
Guidance from <a
href="https://csrc.nist.gov/publications/detail/sp/800-52/rev-2/final">
NIST SP 800-52 Rev. 2
</a> or superceding, MUST be followed for delivery of a `did:web`
document.
</p>
<p>
It is additionally recommended to adhere to the latest recommendations
from OWASP's Transport Layer Protection Cheat Sheet [[OWASP-TRANSPORT]]
for hardening TLS configurations.
</p>
<p>
Consult <a href="https://csrc.nist.gov/publications/detail/sp/800-57-part-1/rev-5/final">
NIST SP 800-57
</a> for guidance on cryptoperiod, which is the time span during which
a specific key is authorized for use or in which the keys for a given
system or application may remain in effect.
</p>
<p>
TLS configuration MUST use at least SHA256, and SHOULD use SHA384,
POLY1305, or stronger, depending on the needs of your
operating environment.
</p>
<p>
Delete action MAY be performed by domain name registrars or DNS lookup
services.
</p>
<p>
As of this writing, TLS 1.2 or higher SHOULD be configured to use
only strong ciphers suites and to use sufficiently large key sizes.
As recommendations may be volatile these days, only the very latest
recommendations should be used. However, as a rule of thumb,
the following set of suites is a reasonable starting point:
</p>
<ul>
<li>
ECDHE with one of the strong curves {X25519, brainpoolP384r1, NIST
P-384, brainpoolP256r1, NIST P-256} shall be used as key exchange.
</li>
<li>
AESGCM or ChaCha20 with 256 bit large keys shall be used for bulk
encryption
</li>
<li>
ECDSA with one of the strong curves {brainpoolP384r1, NIST P-384,
brainpoolP256r1, NIST P-256} or RSA (at least 3072) shall be used.
</li>
<li>
Authenticated Encryption with Associated Data (AEAD) shall be used
as Mac.
</li>
</ul>
<p>
Examples of strong SSL/TLS configurations for now are:
</p>
<ul>
<li>
<code>ECDHE-ECDSA-AES256-GCM-SHA384, TLSv1.2, Kx=ECDH, Au=ECDSA, Enc=AESGCM(256), Mac=AEAD</code>
</li>
<li>
<code>ECDHE-RSA-AES256-GCM-SHA384, TLSv1.2, Kx=ECDH, Au=RSA Enc=AESGCM(256), Mac=AEAD</code>
</li>
<li>
<code>ECDHE-ECDSA-CHACHA20-POLY1305, TLSv1.2, Kx=ECDH, Au=ECDSA, Enc=ChaCha20-Poly1305, Mac=AEAD</code>
</li>
<li>
<code>ECDHE-RSA-CHACHA20-POLY1305, TLSv1.2, Kx=ECDH, Au=RSA, Enc=ChaCha20-Poly1305, Mac=AEAD</code>
</li>
<li>
<code>ECDHE-RSA-AES256-GCM-SHA384, TLSv1.2, Kx=ECDH, Au=RSA, Enc=AESGCM(256), Mac=AEAD</code>
</li>
<li>
<code>ECDHE-ECDSA-AES256-GCM-SHA384, TLSv1.2, Kx=ECDH, Au=ECDSA, Enc=AESGCM(256), Mac=AEAD</code>
</li>
</ul>
</section>
<section>
<h3>
International Domain Names
</h3>
<p>
[[DID-CORE]] identifier syntax does not
allow Unicode in method name nor method specific identifiers.
</p>
<p>
Implementers should be cautious when implementing
support for DID URLs that rely on domain names
or path components that contain Unicode characters.
</p>
<p>
See also:
</p>
<ul>
<li>
<a href="https://unicode.org/reports/tr46/">UTS-46</a>
</li>
<li>
<a href="https://www.rfc-editor.org/rfc/rfc5895">IDNA 2008</a>
</li>
</ul>
</section>
<section>
<h3>
Optional Path Considerations
</h3>
<p>
When optional paths to DID documents are used to resolve documents
rather than bare domains, verification with signed data proves that
the entity in control of the file indicated in the path has the
private keys. It does not prove that the domain operator has the
private keys.
</p>
<p>
This example:
</p>
<pre class="nohighlight">
did:web:example.com:u:bob
</pre>
<p>
resolves to the DID document at:
</p>
<pre class="nohighlight">
https://example.com/u/bob/did.json
</pre>
<p>
In this scenario, it is probable that example.com has given user Bob
control over the DID in question, and proofs of control refer to Bob
rather than all of example.com.
</p>
</section>
</section>
</section>
<section class="appendix informative">
<h1>
Reference implementations
</h1>
<p>
The code at <a
href="https://github.com/uport-project/https-did-resolver">uport-project/https-did-resolver</a>
is intended to present a reference implementation of this DID method. Any
other implementations should ensure that they pass the test suite
described in <code>/src/__tests__</code> before claiming compatibility.
</p>
<p>
The code at <a
href="https://github.com/transmute-industries/restricted-resolver">transmute-industries/restricted-resolver</a>
implements this specification.
</p>
</section>
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